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La Roche calls attention to these facts:-That the ac climated residents of a malarious iocality, while they are less subject than strangers to active fever, show, in their physical and even in their mental organization, evident indications of the ill effects of living in a poisonous atmos phere, an evil which increases with successive genera tions, often resulting in a positive deterioration of the race; that the lower animals are affected, though in a less degree than man; that deposits of organic matter which are entirely covered with water, (as at the bottom of a pond,) are not productive of malaria; that this condition of saturation is infinitely preferable to imperfect drainage; that swamps which are shaded from the sun's heat by trees, are not supposed to produce disease; and that marshes which are exposed to constant winds are not especially deleterious to persons living in their immediate vicinity,—while winds frequently carry the emanations of miasmatic districts to points some miles distant, where they produce their worst effects. This latter statement is substantiated by the fact that houses situated some miles to the leeward of low, wet lands, have been especially insalubrious until the windows and doors on the side toward the source of the miasm were closed up, and openings made on the other side,—and thenceforth remained free from the disease, although other houses with openings on the exposed sides continued unhealthy.

The literature relating to periodical fevers contains noth. ing else so interesting as the very ingenious article of Dr. J. H. Salisbury, on the "Cause of Malarious Fevers," contributed to the "American Journal of Medical Science," for January, 1866. Unfortunately, while there is no evidence to controvert the statements of this article, they do not seem to be honored with the confidence of the profession,— not being regarded as sufficiently authenticated to form a basis for scientific deductions. Dr. Salisbury claims to have discovered the cause of malarial fever in the spores of a very

low order of plant, which spores he claims to have inva riably detected in the saliva, and in the urine, of fever patients, and in those of no other persons, and which he collected on plates of glass suspended over all marshes and other lands of a malarious character, which he examined, and which he was never able to obtain from lands which were not malarious. Starting from this point, he proceeds, (with circumstantial statements that seem to the unprofessional mind to be sufficient,) to show that the plant producing these spores is always found, in the form of a whitish, green, or brick-colored incrustation, on the surface of fever producing lands; that the spores, when detached from the parent plant, are carried in suspension only in the moist exhalations of wet lands, never rising higher, (usually from 35 to 60 feet,) nor being carried farther, than the humid air itself; that they most accumulate in the upper strata of the fogs, producing more disease on lands slightly elevated above the level of the marsh than at its very edge; that fever-and-ague are never to be found where this plant does not grow; that it may be at once introduced into the healthiest locality by transporting moist earth on which the incrustation is forming; that the plant, being introduced into the human system through the lungs, continues to grow there and causes disease; and that quinia arrests its growth, (as it checks the multiplication of yeast plants in fermentation,) and thus suspends the action of the disease.

Probably it would be impossible to prove that the foregoing theory is correct, though it is not improbable that it contains the germ from which a fuller knowledge of the disease and its causes will be obtained. It is sufficient for the purposes of this work to say that, so far as Dr. Salisbury's opinion is valuable, it is, like the opinion of all other writers on the subject,-fully in favor of perfect drainage as the one great preventive of all malarial dis

eases.

The evidence of the effect of drainage in removing the cause of malarial diseases is complete and conclusive. Instances of such improvement in this country are not rare, but they are much less numerous and less conspicuous nere than in England, where draining has been much more extensively carried out, and where greater pains have been taken to collect testimony as to its effects.

If there is any fact well established by satisfactory experience, it is that thorough and judicious draining will entirely remove the local source of the miasm which produces these diseases.

The voluminous reports of various Committees of the English Parliament, appointed to investigate sanitary questions, are replete with information concerning expe rience throughout the whole country, bearing directly on this question.

Dr. Whitley, in his report to the Board of Health, (in 1864,) of an extended tour of observation, says of one town that he examined:

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"Mr. Nicholls, who has been forty years in practice "here, and whom I was unable to see at the time of my visit, writes: Intermittent and remittent are greatly on 66 on the decline since the improved state of drainage of "the town and surrounding district, and more particularly "marked is this alteration, since the introduction of the "water-works in the place. Although we have occasional "outbreaks of intermittent and remittent, with neuralgic "attacks, they yield more speedily to remedies, and are "not attended by so much enlargement of the liver or "spleen as formerly, and dysentery is of rare occurrence." Dr. Whitley sums up his case as follows:

"It would appear from the foregoing inquiry, that in"termittent and remittent fevers, and their consequences, "can no longer be regarded as seriously affecting the "health of the population, in many of the districts, in which "those diseases were formerly of a formidable character.

"Thus, in Norfolk, Lincolnshire, and Cambridgeshire, "counties in which these diseases were both frequent and severe, all the evidence, except that furnished by the 'Peterborough Infirmary, and, in a somewhat less degree, "in Spaulding, tends to show that they are at the present "time, comparatively rare and mild in form,”

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He mentions similar results from his investigations in other parts of the kingdom, and says:

"It may, therefore, be safely asserted as regards Eng"land generally, that:—

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"The diseases which have been made the subject of the present inquiry, have been steadily decreasing, both in "frequency and severity, for several years, and this decrease is attributed, in nearly every case, mainly to one "cause,-improved land drainage," again:

"The change of local circumstances, unanimously de"clared to be the most immediate in influencing the pre"valence of malarious diseases, is land drainage;" and again:

"Except in a few cases in which medical men believed "that these affections began to decline previously to the "improved drainage of the places mentioned, the decrease "in all of the districts where extensive drainage has been "carried out, was stated to have commenced about the same time, and was unhesitatingly attributed to that cause."

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A select Committee of the House of Commons, appointed to investigate the condition and sanitary influence of the Thames marshes, reported their minutes of evi dence, and their deductions therefrom, in 1854. The fol lowing is extracted from their report:

"It appears from the evidence of highly intelligent and "eminent gentlemen of the medical profession, residing in "the neighborhood of the marshes on both sides of the

"Thames below London Bridge, that the diseases preva "lent in these districts are highly indicative of malarious "influences, fever-and-ague being very prevalent; and

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that the sickness and mortality are greatest in those lo"calities which adjoin imperfectly drained lands, and far "exceed the usual average; and that ague and allied dis "orders frequently extend to the high grounds in the vicin"ity. In those districts where a partial drainage has "been effected, a corresponding improvement in the health "of the inhabitants is perceptible."

In the evidence given before the committee, Dr. P. Bossey testified that the malaria from salt marshes varied in intensity, being most active in the morning and in the Summer season. The marshes are sometimes covered by a little fog, usually not more than three feet thick, which is of a very offensive odor, and detrimental to health. Away from the marshes, there is a greater tendency to disease on the side toward which the prevailing winds blow.

Dr. James Stewart testified that the effect of malaria was greatest when very hot weather succeeds heavy rain or floods. He thought that malaria could be carried up a slope, but has never been known to descend, and that, consequently, an intervening hill affords sufficient protection against marsh malaria. He had known cases where the edges of a river were healthy and the uplands malarious.

In Santa Maura and Zante, where he had been stationed with the army, he had observed that the edge of a marsh would be comparatively healthy, while the higher places in the vicinity were exceedingly unhealthy. He thought that there were a great many mixed diseases which began like ague and terminated very differently; those diseases would, no doubt, assume a very different form if they were not produced by the marsh air; many diseases are very difficult to treat, from being of a mixed character